Live hydrocarbon fluids may naturally seep from the seabed, leak from subsea production infrastructure located at the seabed, or flow from subsea well infrastructure at and/or below the seabed. To retrieve live hydrocarbon fluids from shallow water, riser collection systems have been used. In the riser collection system, a riser system or other conduit (hard or flexible) is connected to direct a hydrocarbon source from the seabed to the surface for removal. These systems have primarily focused on shallow water (less than 500 feet) applications and are typically used with low gas content fluids. These systems would be prohibitively expensive for small volumes of hydrocarbon fluids and would be impractical where retrieval occurs at multiple collection points. In addition, these collection systems are not suited for long term operations in remote, deep water fields. In deep water, a passively managed and operated riser collection system is not practical due to the large volume of gas released by the fluid as it ascends and separates within the riser. The rapidly expanding gas inside the riser would require an active gas and pressure management system to be connected to the top of the riser. Further, dynamic forces on the conduit through the water column in operation and during installation contribute to the complexity of the system in deep water applications. Deep water active riser systems exist, but require constant support by a vessel, at high cost, making this solution prohibitively expensive for relatively small volume collection.
Alternatively, subsea sampling systems have been used to retrieve pressurized samples of live hydrocarbon fluids from depth to the surface for laboratory testing. These systems are generally sized for recovery of very small volume (<10 L) samples. Such subsea sampling systems are typically filled with a live hydrocarbon fluid sample at depth where ambient pressure is high, and where the fluids of the sample are pressurized in excess of the ambient pressure. The intent of these systems is to recover the live hydrocarbon fluids to surface at its source's resident pressure (the pressure of the source could be at or even high above the ambient seawater hydrostatic pressure by hundreds to tens of thousands of psi). Trapped pressure of this sort has personnel safety risk implications. Also, the ability to empty the sample and reuse the equipment offshore is limited as it has high internal pressure and would require special depressurization equipment onboard. The methods of these sampling systems are limited to very small volumes and do not inherently allow depressurization before bringing hydrocarbon near personnel. Its primary purpose is to contain the sample and isolate it.
To address the collection and recovery of live hydrocarbon fluids, it would be desirable to provide a system and method for the retrieval of live hydrocarbon fluids from a subsea collection point with the ability to, retrieve fluid to surface in pressurized state, inject collected fluids into existing subsea infrastructure, and/or depressurize the fluid while enacting controlled venting of the gas entrained in the fluid during ascent to the surface from the seabed.